(Record hot temperatures in the lower to middle 80s F [26 to 28 C] spread into the North Slope region of Alaska along the shores of the Arctic Ocean yesterday. And according to Dr. Jeff Masters, the 66 F [19 C] reading at Barrow tied its all time record high. Image source: Brett Brettschneider.)

But extreme heat along the northern reaches of Alaska appears now to be ready to morph into another record heatwave for the lower 48. For the past two weeks, weather models have been consistently predicting severe heat for the Central US. And with each passing day, as the forecasts grow evermore certain, the development of yet one more period of record hot temperatures becomes more and more likely.

An extremely tall dome of hot and heavy air is expected to build up over Colorado, Oklahoma and Nebraska. Heat beneath the dome and near the surface is expected to intensify. By the middle of next week, temperatures over a continuous large swath from Northern Texas to Montana and the Dakotas is predicted to experience near or above 100 degree F (38 C) temperatures. By late week, some of these readings could peak at around 111 degrees Fahrenheit (44 C) for parts of Central Nebraska.

(Saturday, July 24 GFS model forecast shows severe heat settling over the Central US. It’s the kind of heatwave that is now more and more likely to occur due to human-forced climate change. Image source: Pivotal Weather.)

By Sunday, the heat is expected to sprawl both east and west. And high temperatures near or above the Century mark could ultimately stretch in a great triangle from Alabama west to the Central Valley of California and north to Montana’s Canadian Border.

This extreme heat comes in the context of record hot global temperatures. During 2016, global surface temperatures are likely to range near 1.2 degrees Celsius above the late 19th Century average. These record temperatures have been spurred by greenhouse gasses spiking to levels not seen in millions of years. CO2 concentrations this year hit near 408 parts per million at the Mauna Loa Observatory — a level high enough to significantly further increase global temperatures, melt large glaciers, substantially raise sea levels, and prevent another ice age for thousands or tens of thousands of years. And continued burning of fossil fuels by human beings will likely push that number near or above 410 parts per million by May of 2017.

(A North America surrounded by sea surface temperatures in the range of 1-5 C above average is one that is more susceptible to extreme heat, heavy downpours, and drought. Image source: Earth Nullschool.)

Closer to home, very warm sea surface temperatures surrounding the US are likely also aiding in the formation of the predicted heatwave. Hotter oceans surrounding continents can increase the prevalence of heat waves and droughts. And, in this case, 1-5 C above average sea surface temperatures encompass most of North America. In fact, the extent and extreme range of sea surface temperatures — which in the past have rarely exceeded 2 C above average — is notably pretty extraordinary.

These conditions, overall, are less and less impacted by El Nino which has now mostly faded in the Eastern Pacific. As ENSO neutral status now prevails, most temperature extremes are far more related to human-forced warming than El Nino. And, in any case, there’s practically zero chance than any given El Nino year would have resulted in global average temperatures hitting 1.2 C above 19th Century averages without the added heat forcing provided by human greenhouse gas emissions. So the truth of the matter is that the record heat we’re seeing is in greatest part the result of human-forced climate change.